Field of the Invention
The invention relates to a pressure-sensitive adhesive dispersion comprising a water-dispersed polymer P1 formed by emulsion polymerization from a monomer mixture comprising defined C4 to C20 alkyl (meth)acrylates, defined (meth)acrylate monomers with ureido groups or ureido-analogous substituents, acid monomers, and optionally further monomers, the monomer mixture alternatively further comprising glycidyl (meth)acrylate and/or the pressure-sensitive adhesive dispersion comprising at least one further polymer P2 which contains glycidyl groups.
Discussion of the Background
With pressure-sensitive adhesives (PSAs) there is a desire not only for effective adhesion to the substrate but also for sufficient cohesion (internal strength) within the layer of adhesive. Adhesion and cohesion are divergent performance properties. Measures taken to improve adhesion generally lead at the same time to a deterioration in cohesion, and vice versa. Many PSAs, while having sufficient cohesion at room temperature, do not have it at elevated temperatures. Many applications, particularly in the context of adhesive tapes for the fixing of components, as in the automobile sector or the construction sector, for example, nevertheless desire high cohesion even at relatively high temperatures, without too great a deterioration in the adhesion.
WO 01/54896 and EP 822206 describe PSAs comprising polymers which are obtainable by emulsion polymerization and are prepared from, among others, (meth)acrylic monomers with a ureido group. As compared with polymers without ureido groups, these polymers lead to improved shear strength (cohesion) and to improved adhesion even at elevated temperatures. It is desirable, however, to achieve further improvements in the thermal stability of adhesive products based on acrylate polymers. Though aqueous polymer dispersions produced inter alia from (meth)acrylic monomers with a ureido group are also described in EP 710680, they do not constitute pressure-sensitive adhesives.